iPod Super
Here is a nice article written by Collin Allen about how to Interfacing 3.5โ€ณ hard drive with the iPod he writes:
This project came about after I dropped my 40 GB 3rd generation iPod and killed the hard drive in it. I decided to open up the iPod and see what I could do with it. I could do so without fear of breaking it, since Iโ€™d already broken the most expensive part in it.

   iPod Super - Interfacing 3.5โ€ณ hard drive with the iPod
at www.command-tab.com